The present invention relates to an electrophotographic apparatus such as an electrostatic copying machine comprising an improved optical imaging system which utilizes a focussing optical fiber array as a main converging element.
Focussing optical fiber arrays have been recently developed and offer a number of advantages when incorporated into electrophotographic apparatus such as electrostatic copying machines, facsimile devices and the like. Such optical fiber arrays provide and erect image with unity magnification.
However, due to the configuration of the scanning systems in such apparatus, it is sometimes desirable to provide an inverted, rather than an erect image. This is because it is advantageous to have the various elements of the scanning systems move in certain directions relative to each other.
One simple means of obtaining an inverted image is to reflect the image once by means of a plane mirror or triangular prism. However, image distortion occurs unless the image plane is substantially perpendicular to the object plane, and it is practically impossible to make the image and object planes parallel. Where an original document for electrophotographic reproduction is advantageously supported by a horizontal document carrier or platen, it is necessary to move a photosensitive element vertically for scanning. This creates a disadvantageous geometric arrangement of the optical system in the apparatus and leads to increased complexity, size and manufacturing cost. The use of a trapezoidal prism introduces astigmatism and degradation of the optical resolving power to an unacceptable extent.